1. Field of the Invention
The present invention relates generally to a composite type piezoelectric component combining a piezoelectric device with a capacitor, and more particularly, to a composite type piezoelectric component used as, for example, an oscillator containing load capacitances.
2. Description of the Prior Art
FIG. 9 shows one example of a conventional composite type piezoelectric component used as an oscillator containing load capacitances.
The composite type piezoelectric component shown in FIG. 9 has a piezoelectric oscillating device 2 structured such that electrodes 22 and 23 are individually formed on the mutually opposite two major surfaces of a piezoelectric substrate 21 in a long narrow rectangular plate shape. The electrodes 22 and 23 are respectively formed so as to extend from one end of the piezoelectric substrate 21 towards but without reaching the other end thereof. In addition, both the electrodes 22 and 23 are opposed to each other through the piezoelectric substrate 21 in the center of the piezoelectric substrate 21.
First and second terminals 3 and 4 are respectively joined by solder to ends of the piezoelectric oscillating device 2 constructed as described above. More specifically, respective top ends 31 and 41 of the first and second terminals 3 and 4 are formed in a semicylindrical shape, and the ends of the piezoelectric oscillating device 2 are received respectively in these semicylindrically shaped top ends 31 and 41. The electrodes 22 and 23 of the piezoelectric oscillating device 2 are respectively soldered to the top ends 31 and 41 of the first and second terminals 3 and 4 with the ends of the piezoelectric oscillating device 2 respectively received inside the ends 31 and 41 of the first and second terminals 3 and 4. For easy understanding, illustration of solder is omitted in the drawings appended to the present specification.
A capacitor 6 is fixed to the outside of the top ends 31 and 41 of the above first and second terminals 3 and 4. As shown in FIGS. 10A and 10B, the capacitor 6 in structured such that an electrode 62 is formed to cover a relatively large area on one major surface of a dielectric substrate 61 in a long narrow rectangular plate shape and a pair of electrodes 63a and 63b divided in the center is formed on the other major surface thereof. In FIG. 9, the capacitor 6 is fixed to the first and second terminals 3 and 4 by respectively soldering the divided electrodes 63a and 63b to outer surfaces of the top ends 31 and 41 of the terminals 3 and 4. Accordingly, in this oscillator containing load capacitances, a clearance which is large enough for not preventing the vibration of the piezoelectric oscillating device 2 is provided between the capacitor 6 and the piezoelectric oscillating device 2.
A top end of a stripe-shaped third terminal 5 is soldered to the electrode 62 on the other major surface of the capacitor 6.
In the above described oscillator containing load capacitances, capacitances are formed between the electrode 62 and the electrodes 63a and 63b on the capacitor 6. Consequently, an equivalent circuit of the oscillator containing load capacitances is as shown in FIG. 11. Such an oscillator containing load capacitances has been suitable for the use for, for example, a Corpitts type oscillating circuit.
In the capacitor 6 used in the above described oscillator containing load capacitances, however, the electrodes formed on the major surfaces thereof differ from each other in shape. In other words, a defective product would result if wrong major surfaces of the capacitor 6 were inadvertently attached to the terminals 3 and 4 in a step of fabrication. Therefore, in joining the capacitor 6 to the terminals 3 and 4, it was necessary to preliminarily ascertain the directionality of the capacitor 6 or to distinguish between its two major surfaces by means of a machine. Thus, the prior art fabrication process was disadvantageously complicated.